Competition of electron transfer, dissociation, and bond-forming processes in the reaction of the CO22+ dication with neutral CO2

Abstract

The bimolecular reactivity of the CO₂²⁺ dication with neutral CO₂ is investigated using triple quadrupole and ion–ion coincidence mass spectrometry. Crucial for product analysis is the use of appropriate isotope labelling in the quadrupole experiments in order to distinguish the different reactive pathways. The main reaction corresponds to single-electron transfer from the neutral reagent to the dication, i.e. CO₂²⁺ + CO₂ → 2CO₂⁺; this process is exothermic by almost 10 eV, if ground state monocations are formed. Interestingly, the results indicate that the CO₂⁺ ion formed when the dication accepts an electron dissociates far more readily than the CO₂⁺ ion formed from the neutral CO₂ molecule. This differentiation of the two CO₂⁺ products is rationalized by showing that the population of the key dissociative states of the CO₂⁺ monocation will be favoured from the CO₂²⁺ dication rather than from neutral CO₂. In addition, two bond-forming reactions are observed as minor channels, one of which leads to CO⁺ and O₂⁺ as ionic products and the other affords a long-lived C₂O₃²⁺ dication.